Fortuitously, the laboratory across the hall from mine was occupied by a man whose name is David Kritchevsky. David is a wonderful personality, with a tremendous sense of humour. He lived close to me and, indeed, we... he picked me up each morning in his automobile and carried me to the Wistar Institute and I returned home with him because his house was a few miles beyond mine; very convenient for him to meet me and drop me off. Of course, I shared the expenses.

We rode together in his car for several years, which was a very nice experience due to David's marvellous sense of humour, analysis of people. He was not a cell culturist; he was a lipid chemist with a worldwide reputation. And through his lipid chemistry experiments, he dealt with media formulation of different lipid constitutions in feeding the rabbits that he was using for his experiments on cholesterol and other lipids.

Each... each of these media formulations was... was made for him by a company who compounded the chemicals into a tablet that was edible by rabbits. That was significant because during one of our automobile trips I told David about my problem and I said, what I.... I said, 'What I would like to do is the following.' I said, 'I know that this is heresy in respect to how cell culture media has been produced up to this day, but I want to do the following.' And before I tell you what the following is, I need to explain what was done up until that day in respect to media preparation. It was, in fact, almost an art form because there were different salts, different amino acids, and other components that had to be mixed together. If you did it all at once, it was argued, they would precipitate and you would get inactive components. You had to prepare the media in blocks of chemicals prepared as separate blocks, carefully, then mixed together at different temperatures; a very complex way of producing the media so that it turned that all of the components will be saleable.

Getting back to my car... my... and this was a kind of black magic. I have records from cell culture courses that consist of two or three pages of how you compound cell culture media. I said in my ignorance to David one day, 'Why can't – he was after all a major chemical chemist – why can't I take these... all these components, put them in a mortar and pestle, grind them up very fine, add water, and have my media?' He said, 'Hayflick, it's apparent to me that you've never had a course in physical chemistry, because that won't work. Those elements will precipitate.'

Leonard Hayflick (b. 1928), the recipient of several research prizes and awards, including the 1991 Sandoz Prize for Gerontological Research, is known for his research in cell biology, virus vaccine development, and mycoplasmology. He also has studied the ageing process for more than thirty years. Hayflick is known for discovering that human cells divide for a limited number of times in vitro (refuting the contention by Alexis Carrel that normal body cells are immortal), which is known as the Hayflick limit, as well as developing the first normal human diploid cell strains for studies on human ageing and for research use throughout the world. He also made the first oral polio vaccine produced in a continuously propogated cell strain - work which contributed to significant virus vaccine development.